Lewis Rothstein
URI Graduate School of Oceanography
Professor; physical oceanography

The ocean, with the ebb and flow of tides, currents swirling at and beneath the surface, and winds blowing overhead, never stills, even at its calmest moments.

This constant state of circulation, says Lewis Rothstein, determines the health of our coastal system, which, in turn, supports the food web, drives the economy, and sustains quality of life.

The balance that is the earth’s heat budget — whether purely natural or influenced by human actions — determines how and where the water moves, and affects such characteristics as the light penetration and food availability organisms depend on for survival.

“The overall focus of my research is trying to understand the flow of energy through the world’s oceans, “ Rothstein explains. “How is the coastal regime responding to natural climate variability and the trend that is climate change?”

Awarded a series of three, interrelated RI Science and Technology Advisory Council (STAC) grants, Rothstein and his peers in the Rhode Island NSF EPSCoR community are creating numerical models guided by observed scientific data to forecast the impact of climate change on water movement and the implications for marine life and ecosystems.

Says Rothstein: “We have to understand how the ocean circulates. The foundation of our coastal ecosystem — from the tiniest of organisms to fish — lies in how the water responds within a world that is experiencing profound climate change.”

He explains that for models to focus detailed attention on a particular region such as Rhode Island Sound, which is found within a much larger region (the U.S. Northeast shelf/slope coastal waters), scientists use a computational technique called nested-grids. Essentially, these are a sequence of overlapping grid systems implemented on a computer to accurately represent the variability of the particular region while accounting for the influence of the much larger region.

With increased understanding, RI EPSCoR scientists can help Ocean State policy makers and citizens better manage natural resources and prepare for future scenarios while contributing valuable, novel approaches applicable elsewhere.

The teams employ a process called hindcasting to test the accuracy of their models, going back in time, say to a period from 1990-2005, and utilizing data and observations already documented to see if the models reliably predict what already happened in 2010.

The researchers then can apply the models with confidence to future projections, building increasingly higher resolution and more detailed numerical grids specific to bodies of water large (the north Atlantic coast) or small (Narragansett Bay and Block Island Sound) to solve equations. They vary the values of relatively uncertain quantities (for example, ocean mixing) to better gauge how shifts in the ecosystem will produce what biogeochemical changes.

But, the models are guided by more than a random variation of these quantities, explains Rothstein. They are fed and informed by observations, too, allowing researchers to take what they know of physics, and the biology and chemistry of lower trophic levels, and use the models to extrapolate the impact out to the higher trophic levels. They can take climate change projections from the Intergovernmental Panel on Climate Change (IPCC), run them through the global models and impose the information on Rhode Island grids to see how the system reacts to a changing climate.

“These grants have been unique for me. They are significant in that they are a bridge to establish new connections. And, they’ve given me a better sense for how my work fits with Rhode Island needs.”

This kind of work showcases what Rhode Island EPSCoR has meant to both research and scientists in the state, according to Rothstein. The STAC grants, which constitute the state’s match to the federal dollars, provide crucial seed funding to secure data and develop more sophisticated models for more substantial grants, to ask new and bigger questions, and support graduate assistantships to train young scientists.

Together, RI EPSCoR and STAC have provided new opportunities for collaboration across partner institutions, tapping into ideas and talent that drive groundbreaking projects like the ocean modeling of the state’s coastal waters. Rothstein says he hadn’t worked with anyone in Rhode Island outside the GSO prior to the EPSCoR grant.

Additionally, RI EPSCoR-supported core facilities have increased capacity, allowing scientists to conduct research that they otherwise would not be able to pursue. The findings have been published in premier publications and furthered the body of science.

“I’ve been well funded by the National Science Foundation, NOAA, NASA, DHS and DOE,” Rothstein says. “I’ve been in this business for 30-something years. But, these grants have been unique for me. They are significant in that they are a bridge to establish new connections. And, they’ve given me a better sense for how my work fits with Rhode Island needs.”

The next step for this group of collaborators is a grant proposal that will pair the numerical models and health data for Narragansett Bay shellfish to investigate what is taking place at the lower trophic level and document the connection to the higher trophic levels.

In doing this, the paradigm will shift in how scientists can relate the full marine ecosystem across all trophic levels to physics, an effort that Rothstein calls the grand challenge of the field: “That is the holy grail of full marine ecosystem forecasting and modeling.”

The question for RI EPSCoR researchers is why? Why do the shellfish get sick? What events occurred? How do we understand climate change and variability? How do we forecast the outcomes and manage our fisheries?

He explains: “You have diseased shellfish, the disease being a function of their environment, which includes the physics, temperature of the water, salinity, and various chemical constituents. Their health also is a function of the lower trophic level, the health of what they feed on. Any variability and they may have a hard time dealing with it and could get sick. This has happened.”

The question for RI EPSCoR researchers is why? Why do the shellfish get sick? What events occurred? How do we understand climate change and variability? How do we forecast the outcomes and manage our fisheries?

Undoubtedly, climate change and variability impact the morbidity and mortality of shellfish, and the outcome will affect such critical resources as Rhode Island fisheries, tourism, and drinking water.

“What happens here,” Rothstein says, pointing to the direction of water movement within a grid that stretches well beyond the Rhode Island coast, “impacts the shellfish in Narragansett Bay.”

Story and photo by Amy Dunkle | RI NSF EPSCoR